The invention relates to the problem of adaptive data detection in a mobile radio receiver. "Adaptive" means that there is provided in the receiver a device which can track the temporal changes in the characteristics of the mobile radio channel. Such devices mostly operate using the LMS (Least Mean Squares) (see [1] for example) or the RLS (Recursive Least Squares) (see [2], for example) algorithm. These algorithms adapt to the characteristics of the transmission channel continuously with time. For example, a Kalman filter for adapting the channel unit pulse response in a mobile radio receiver is described in Fifth European Signal Processing Conference, 18-21/9/1990, Barcelona, ES; elsevier, Amsterdam, NL, 1990; pages 225-228, Morgul & Dzung: "New optimum recursive parameter estimation/detection using unreliable erasure-declaring detector". In this case, the Kalman algorithm is applied only to the channel unit pulse response present at a specific instant.
EP-A-0 524 597 includes a description of an iterative method for reducing intersymbol interference, in which the value of received sample values is fixed after one or more plausibility thresholds have been passed. The intersymbol interference is suppressed with the aid of the respective deviations of the received sample values from the fixed values.
EP-A-520 969 includes a specification of an estimation method for data detection, in which received sampled values of a time slot are initially stored, starting with the value first received, and processed, specifically as far as beyond a fading dip; further processing is then performed starting with the sampled value last stored, in order to generate estimated values of the transmitted data.
It is demonstrated in this patent application that continuously adapting algorithms fail under certain conditions which are typical of mobile radio. The reason for this is that the above need adaptation algorithms can be regarded as time-variant recursive filters of the first order. Higher order algorithms exhibit a better behaviour in principle; two possible algorithms are described in [3] and [4]. A precondition for these algorithms is a reliability-controlled data detection, that is to say in a specific received signal segment the data bits are detected not in continuous sequence with time but, starting with the most reliable data bits, in the direction of decreasing reliability.